Dozer impresses in mine trials

The Wilpinjong coal mine is an open cut mine located 40km northeast of Mudgee, New South Wales. The mine is owned and operated by Peabody Australia and is one of the lowest cost thermal coal mining operations in Australia. The mine provides coal for domestic generators and exports to customers in the Asia-Pacific region. Currently the mine produces more than 13 million tonnes of coal per annum and employs more than 400 workers.

The mine has contributed 35 per cent towards Peabody’s improvement in the global safety rate since 2012, and in 2016 it generated $750 million of direct and indirect benefits to the economy. Peabody restored/rehabilitated more than 2000ha of coal-mined land in 2017. Being an open cut mine, Wilpinjong uses trucks, shovels, castings and dozers in its mining operations.

The Liebherr PR 776 hydrostatic drive bulldozer arrived at Wilpinjong with 3500 hours in March 2017, completing an additional 2500 operating hours to August 2017, with machine availability averaging 94 per cent. Equipped with a 22m3 U-blade and single shank ripper, the PR 776 conducted general applications ranging from dump push, to cleaning excavator floors, and bulk push. The machine generated a keen interest for a comparative test trial against a 70-tonne class dozer in the Wilpinjong fleet.

Overall, feedback from the operators was positive and the ability of the dozer to push heavy loads without issues was a common theme. Test parameters were agreed, with the objective to compare the hydrostatic PR 776’s performance against a class competitor from the mine site’s established mechanical drive fleet. Test parameters included:

  • Time taken to push off bulk quantity of material. The mine plan was set up for a dumpsite where tight dump of bulk load of material was pushed, and a drone flying overhead measured bank cubic metres (BCMs) moved by each machine.
  • Comparison of manoeuvrability. By dumping series of loads across the tip head at a set distance from the edge, parameters tested time taken to move the series load by each machine and how the ground base was disturbed and traction achieved.

Mine trials – Test 1

In order to commence trials, a mine plan was prepared to have a test area with flat ground. The requirements of testing were to use one machine after the other using the same operator, providing a real world scenario of dozer operations in a mine site.

Peabody’s Liebherr R 9400 excavators loading 180-tonne class trucks dumped two sets of loads. Each set was placed 15m from the dump edge, with five loads in series, followed by a further two sets of six loads, and a survey drone measured the amount of material in both sets of loads before and after. One service truck was used for both machines before and after the test, with fuel consumption measured at the service truck meter reading and from the operator cab.

The survey drone measured:

  • PR 776: 1821 BCM at 1.8 tonnes per cubic metre (t/m3) – or 3278 tonnes – in the first heap pushed in two hours and 44 minutes.
  • Competitor: 1791 BCM at 1.8 t/m3 – or 3224 tonnes – in the second heap pushed in two hours and 43 minutes.
  • The PR 776 completed the task a minute slower than the competitor machine but this time was attributed to the extra 54 tonnes it pushed.

Fuel consumption readings from the on-board computers showed:

  • PR 776: Two hours and 44 minutes operating hours at 92 litres per hour and fuel consumption of 253 litres.
  • Competitor: Two hours and 43 minutes operating hours at almost 115 litres per hour and fuel consumption of 311 litres.

Mine trials – Test 2

The second test comprised two parts:

Part A – Cleaning the dump site where the haul truck dropped six loads in series, five metres from the dump edge for each machine, and time taken for each machine to clear the load. The PR 776 finished the task 90 seconds slower than the competitor machine but it completed the task in 36 passes, three less than the competitor. This test showed the PR 776 could move more tonnes per pass.

Part B – Testing the agility of the machine and its ability to turn/steer (instead of move) with full load. During this test, the advantage of a hydrostatic machine over mechanical drive was clearly visible. The PR 776 moved easily with a full blade and could carry material, whereas the mechanically driven machine struggled to manoeuvre under full load, and spilled a considerable amount while trying to both manoeuvre and move forward.

At the completion of the Part A and B tests, a service truck filled the two machines. The truck meter reading showed the PR 776’s fuel consumption for the test. To push 36 full blades of pass over the dump edge and to carry out the agility test, the PR 776 consumed 17 fewer litres than the competitor’s machine.



Meeting targets

Operator feedback on key performance indicators and capabilities were noted over the test period. The PR 776 had the ability to push load and manoeuvre under a fully loaded blade, and complete the manoeuvrability test quicker than its competition. The Liebherr on-board computer readings were closer to the service truck readings. A further advantage of the Liebherr system was that live data could be conveyed on the operator’s screen, whereas the data on the competitor’s machine had to be downloaded to a computer first.

All tests showed comparable performance but the Liebherr PR 776 exceeded expectations, with 19 per cent less fuel consumption.

The results showed that the PR 776 is a strong contender with enhanced operator visibility, manoeuvrability, and a better fuel consumption rate, providing the user with a comprehensive product to meet production targets efficiently.

The 72-tonne PR 776 is part of Liebherr’s crawler dozer range – which includes the 38-tonne PR 756 and 46-tonne PR 766.

Source: Liebherr Australia

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